Another day, another complete whackjob surfaces from the liberal side. You really cannot make this stuff up.

Another day… Another attack on the “deniers.”

Radical, nutty, propagandist Professor Kari Norgaard has followed the lead of all the other Liberals who can’t use data and facts to win their argument. Professor Norgaard, from the University of Oregon, says to deny Global Warming junk science is “racism.” But, it’s even more absurd than that. If you reject the junk data, corruption, and blatant grab for power that is the Green Movement she wants you diagnosed with a disease. And treated.

Scepticism regarding the need for immediate and massive action against carbon emissions is a sickness of societies and individuals which needs to be “treated”, according to an Oregon-based professor of “sociology and environmental studies”. Professor Kari Norgaard compares the struggle against climate scepticism to that against racism and slavery in the US South.

‘Resistance at individual and societal levels must be recognized and treated …

“This kind of cultural resistance to very significant social threat is something that we would expect in any society facing a massive threat,” [Norgaard] said.

The discussion, she said, is comparable to what happened with challenges to racism or slavery in the U.S. South.’

Kari Norgaard doesn’t understand the basics of the scientific principle. Even accepted science is constantly critiqued…it’s lesson number 1. Real scientists rigorously try to disprove their theory and welcome outside criticism as a way of bolstering the truth behind the science. But, Kari Norgaard wouldn’t know that, because her only science degree is a Bachelors. What she is practicing is social science, which is just Liberalism dressed up as science.

It is a mental disorder, to believe humans can change the climate, there is only one who controls all things. He is the only God of the universe. He is the one who lets the sun shine on our faces. He makes the rain fall on his command. He decides when and where there shall be earthquakes. He causes the oceans to react violently or calmly. He is the almighty who does whatever he needs to do, to accomplish his prophesies. Global warming is a big myth made up by the corrupt liberals.

Global warming denial is a propaganda campaign funded by the corporations whose products bear the largest responsibility for the problem - i.e. coal, oil and gas producers. The aim is to protect their profits from attempts to reduce emissions of carbon dioxide and thus mitigate global warming.

The catastrophic man-made global warming hypothesis has failed. The sun controls our climate in all broad terms and any effects of CO2 are simply matters of minor changes of the distribution of temperatures within the atmosphere. These effects are so small that scientists have been unable to measure them! All claims of an effect are based on computer models which are known to be insufficient in their inputs and wrong on many critical predictions. These models do not agree well with one another, further indicating an insufficient understanding of the basic science of the climate and the earth, ocean, atmosphere, and solar systems. It is both rational and important that we view any claims of catastrophic man-made global warming as unproven and improbable.

You said "The sun controls our climate in all broad terms" but the evidence shows that variations in solar output are actually very small and have only a minor effect on global climate. Variations in volcanism have a larger effect, and are probably the main cause of climate changes such as the 'Mediaeval Warm Period' and the 'Little Ice Age'. Orbital variations have far more effect, causing ice ages and interglacials. However, the biggest controller of global climate is atmospheric CO₂, since it is responsible for 80% of the forcing which sustains the greenhouse effect and keeps the Earth from turning into an iceball¹. Since we are now in control of atmospheric CO₂, that means we're now in control of global climate. It took us just 250 years to exert the same climate forcing with our output of greenhouse gases as the sun took 125 million years to achieve with its long slow warming trend.

Statements that the solar radiation varies little are based on a very short timescale and generally fail to note that the high energy ultraviolet portion of the spectrum varies much more than the visible portion. There is also a failure to deal with the large variations in solar magnetic field and the solar wind. Note also that changes of orbit are important because they change solar radiation fluxes upon the Earth.

Water vapor is the important infra-red absorbing gas, not CO2. The CO2 effect is at most very weak and every model that claims it is of any significance at all does so upon the false claim that it has a positve feedback from water vapor so that most of any temperature increase is due to water vapor. If we had no CO2 and no water vapor, the Earth would not be an iceball. Most of the Earth land surface would be so hot every afternoon that humans would die from the heat if caught outside in direct sunlight. If we had water vapor, but no CO2, the Earth's temperature would be very little changed. If CO2 made much difference at all, we would be able to measure the increased temperature at 8 to 12 km altitude over the tropics and low latitudes that the computer models say should be there, but is not.

Interesting. TSI of course includes UV so it could be that solar irradiance is more important relative to volcanic forcings than I thought. However, anthropogenic forcings are now *much* larger than the solar forcing -

... and of course we know that TSI and global temperature have been going in opposite directions for the last 50 years or so -

Yes, the link did work this time. First, comments on your NOAA graphs. I have very little confidence in the accuracy of most of the forcing strengths given. That lack of confidence is borne of the difficulty of actually separating out any effect from experimental data and the difficulty of getting accurate theoretical results when such effects of CO2 are so little understood that in 2010 those who claimed the science was settled for more than a dozen years announce that without CO2, water vapor cannot sustain a greenhouse effect!

Now, let us look at the temperature v. Solar Activity plot. You say they are going in opposite directions for the last 50 years. Yes, but you have to think about the physics here to understand that a rising temperature is implied by the solar activity shown in that time. Broadly speaking, from 1880 to 1960, the solar activity rose, then since then it has fallen very slightly. Recall that the oceans hold most of the heat content near the surface of the Earth and that if there were a sudden increase in solar activity to a new plateau level, the oceans would take hundreds of years to equilibrate at a new higher temperature. The temperature of the oceans and their total heat content would be rising throughout that time. Apply that simple case to th...

Yes, the link did work this time. First, comments on your NOAA graphs. I have very little confidence in the accuracy of most of the forcing strengths given. That lack of confidence is borne of the difficulty of actually separating out any effect from experimental data and the difficulty of getting accurate theoretical results when such effects of CO2 are so little understood that in 2010 those who claimed the science was settled for more than a dozen years announce that without CO2, water vapor cannot sustain a greenhouse effect!

Now, let us look at the temperature v. Solar Activity plot. You say they are going in opposite directions for the last 50 years. Yes, but you have to think about the physics here to understand that a rising temperature is implied by the solar activity shown in that time. Broadly speaking, from 1880 to 1960, the solar activity rose, then since then it has fallen very slightly. Recall that the oceans hold most of the heat content near the surface of the Earth and that if there were a sudden increase in solar activity to a new plateau level, the oceans would take hundreds of years to equilibrate at a new higher temperature. The temperature of the oceans and their total heat content would be rising throughout that time. Apply that simple case to the data you presented from NOAA. The average solar activity from 1960 to about 2005 was higher than it was in 1950, which was substantially higher than it had been going back to 1880. So, this higher average temperature for 50 years would be acting on the oceans which had cooled during the Little Ice Age prior to 1880 and continue to heat the oceans up, even as the solar activity fell ever so slightly in the last 50 years. There is no contradiction here at all. Even the rock and soil of the land will be doing something similar. The heat content of the oceans and the rock and soil are very important in evening out the Earth's temperature on the daily cycle, the seasonal cycle, and over periods of years and even hundreds of years.

It's true that we can't have as much confidence in pre-industrial TSI as we can in today's instrumental data, which is why there is a range of up to several tenths of a Watt in some parts of the record (part (b) of the graph above), but today we have accurately known anthropogenic forcings which are *much* larger - 2.4W/m² for greenhouse gases, for example, which is 1% of incident solar irradiance. The sun took 125 million years to increase its output by 1% according to solar physicists - there's no sign in the geological record of that magnitude of variation in just a few years, decades or centuries. Any delayed solar warming due to the thermal inertial of the oceans would still be much smaller than the current anthropogenic warming, and in fact numerous studies show that natural forcings should have been producing a slight cooling trend for the last 50 years or so - Meehl et al 2004, etc.

Cloud cover variations as a result of solar activity variations appear to be substantial multipliers of that variation. The claimed 1% rise in solar activity over 125 million years will be a long term response averaged over shorter term fluctuations. The record will not likely tell us much about the shorter fluctuations.

A study showing a slight cooling trend, if the plot you presented is right, makes no physical sense. Many studies are poorly conducted and or poorly interpreted. I have rejected many a paper I have refereed as a result, though other referees accepted the garbage.

First of all, the result claimed that CO2 is the Earth's thermostat and that water vapor alone would produce no greenhouse effect is based upon the very same computer models that predict an atmospheric thermal gradient that contradicts experimental measurements. Those models assume a large positive feedback of water vapor to any CO2 greenhouse effect and to date all actual measurements are producing virtually no feedback or even a negative feedback. The negative feedback is consistent with a more stable climate system and we have pretty good reason to believe the Earth is a pretty stable system. Having pointed out fatal flaws in the computer models, we are now going to trust the same model to tell us that water vapor alone has no greenhouse effect, but CO2 working with it does?

This is a startling claim given that for a dozen years prior to this climate science was said to be settled. If this basic relationship between CO2 and water vapor was not understood, what other basic physics that needed to be incorporated into the computer models for them to make correct predictions were not understood? How is it that CO2 manages to keep water vapor from precipitating? Is it because they assumed the same strong positive feedback between increased CO2 and water vapor that allowed t...

First of all, the result claimed that CO2 is the Earth's thermostat and that water vapor alone would produce no greenhouse effect is based upon the very same computer models that predict an atmospheric thermal gradient that contradicts experimental measurements. Those models assume a large positive feedback of water vapor to any CO2 greenhouse effect and to date all actual measurements are producing virtually no feedback or even a negative feedback. The negative feedback is consistent with a more stable climate system and we have pretty good reason to believe the Earth is a pretty stable system. Having pointed out fatal flaws in the computer models, we are now going to trust the same model to tell us that water vapor alone has no greenhouse effect, but CO2 working with it does?

This is a startling claim given that for a dozen years prior to this climate science was said to be settled. If this basic relationship between CO2 and water vapor was not understood, what other basic physics that needed to be incorporated into the computer models for them to make correct predictions were not understood? How is it that CO2 manages to keep water vapor from precipitating? Is it because they assumed the same strong positive feedback between increased CO2 and water vapor that allowed them to multiply the weak CO2 greenhouse effect of their models by a factor of 3 or more due to increased water vapor concentrations in the atmosphere and therefor an increased temperature contribution due to water vapor?

As you can see, I consider this a very questionable result. The key factor has to be actual measurements of the feedback response of water vapor to CO2 increases. I think it very unlikely that an atmosphere without CO2 would have drastically less water vapor in it.

"the result claimed that CO2 is the Earth's thermostat and that water vapor alone would produce no greenhouse effect"

It doesn't say that at all. What it says is that (obviously) the non-condensing greenhouse gases sustain the greenhouse effect, because in their absence most water vapour would precipitate out as rain and snow. Water vapour is a significant greenhouse gas - about one quarter as effective as CO₂ - but it's only there in the atmosphere in such quantities because CO₂ and other non-condensing GHGs sustain the forcing that allows it to be there.

By 'atmospheric thermal gradient' I assume you're talking about the tropical tropospheric hot spot, but that is an expected consequence of global atmospheric warming, *regardless* of its cause - it's not a signature of *anthropogenic* warming per se.

The reason is fairly straightforward: As air rises and cools, the water vapour in the air cools enough to condense out as clouds, and in doing so releases latent heat (this is a fundamental physical phenomenon associated with condensation). This latent heat offsets some of the cooling of the rising air.

In the tropics, where the atmosphere holds more moisture, proportionally more heat should be released, so the offsetting of cooling at altitude should be greater - i.e. we should...

"the result claimed that CO2 is the Earth's thermostat and that water vapor alone would produce no greenhouse effect"

It doesn't say that at all. What it says is that (obviously) the non-condensing greenhouse gases sustain the greenhouse effect, because in their absence most water vapour would precipitate out as rain and snow. Water vapour is a significant greenhouse gas - about one quarter as effective as CO₂ - but it's only there in the atmosphere in such quantities because CO₂ and other non-condensing GHGs sustain the forcing that allows it to be there.

By 'atmospheric thermal gradient' I assume you're talking about the tropical tropospheric hot spot, but that is an expected consequence of global atmospheric warming, *regardless* of its cause - it's not a signature of *anthropogenic* warming per se.

The reason is fairly straightforward: As air rises and cools, the water vapour in the air cools enough to condense out as clouds, and in doing so releases latent heat (this is a fundamental physical phenomenon associated with condensation). This latent heat offsets some of the cooling of the rising air.

In the tropics, where the atmosphere holds more moisture, proportionally more heat should be released, so the offsetting of cooling at altitude should be greater - i.e. we should see a 'hot spot' in lower latitudes compared to higher latitudes. There is in fact some evidence of this over short intervals (months to a year), but the evidence is less clear for longer intervals.

Logically, this does not in itself cast doubt on anthropogenic warming or the accuracy of the models you mention, since we have abundant evidence from land and ocean measurements, balloon measurements, satellite measurements and many thousands of other physical and biological metrics that the climate is indeed warming. The lack of firm long-term evidence for a tropical tropospheric hot spot doesn't cast doubt on the models and is far more likely to be due to the inadequacy of measurement systems which are primarily designed for weather forecasting rather than climate science research.

Both palaeoclimate data and modern observations overwhelmingly argue against predominantly negative feedbacks. If there was a large net negative feedback then it would be very hard to explain the large (~5°C) global warming of the last deglaciation from the very small (~0.25W/m²) solar forcing. Of course, if you argue that 0.25W/m² of forcing can produce a warming of 5°C even with net negative feedbacks then you're arguing for an absolutely huge climate sensitivity of 20°C/W/m², which would mean that the 1.6W/m² of anthropogenic forcing to date would be expected to produce 32°C of global warming and leave most of the planet uninhabitable for anything except micro-organisms. I don't know of anyone who thinks that's going to happen.

One thing we can do is estimate the magnitude and sign of feedbacks (i.e. climate sensitivity) from modern data. Over the period 1900 to 2010, CO₂ rose from 290 to 380ppm. The 'no-feedback' warming would therefore be calculated as follows:

ΔF = 5.35 * ln(C/C₀) = 5.35 * ln(380/290) = 1.44W/m²

ΔT = ΔF * 0.27 (because as everyone agrees, the 'no feedback' warming from CO₂ is about 1°C from a doubling of CO₂, and a doubling of CO₂ is a forcing of about 3.7W/m², hence the no-feedback climate sensitivity would be 1/3.7 = 0.27°C/W/m²).

ΔT in this scenario is therefore 1.44 * 0.27 = 0.39°C at equilibrium. Climate inertia (thermal inertia of the oceans) means that we would expect to see about 60% of that in 2010, i.e. about 0.23°C. In reality we have seen rather more warming in the period than that - 0.7°C, about 3 times as much.

So the existence of large positive feedbacks from factors such as clouds and water vapour is supported by this data as well - in fact, a factor of 3 is precisely what climate scientists are citing as the best estimate for fast feedback climate sensitivity, from numerous different studies. Net negative feedbacks just do not accord with what we know about climate at all.

Water vapor has a much greater IR absorption effect than CO2 and its effect is commonly not near saturation, so it is not clear how you are claiming CO2 to be a more effective greenhouse gas. Is this because you subtract out the counterbalancing effects of water condensation and evaporation that you are making this claim? In any case, note that I did not say that water vapor does not absorb IR or any such thing. I said that a consequence of the paper was that it could not remain as water vapor in the atmosphere sufficient quantity to act as the greenhouse gas it has so long been claimed to be.

The solar radiation effects assumed in your argument are not valid. Where do you get the 0.25 W/m2 value in the last glaciation? What is the source of the factor 5.35 in ΔF = 5.35 * ln(C/C₀)? Note that the change of CO2 concentration since 1900 is not all due to man. The claim that the 'no feedback' warming from CO₂ is about 1°C from a doubling of CO₂ is not universally agreed to, though many seem to like that number. Then you assume that all of the warming of 0.7C is due to effects of CO2, which is quite an assumption.

No one I know of is claiming a large negative feedback from water. As I clearly said, feedback has been measured as very nearly zero of a small negative feedback.

Water vapour is responsible for ~50% of the *current* greenhouse effect with CO2 at ~20% ( Schmidt et al 2010 ).

However, there is 10 times more water vapour than CO₂ in the atmosphere, so by my reckoning CO₂ is 4 times more effective as a greenhouse gas than water vapour. Part of that is because water vapour is largely confined to the troposphere whereas CO₂ is well-mixed throughout the atmosphere.

"I said that a consequence of the paper was that it could not remain as water vapor in the atmosphere sufficient quantity to act as the greenhouse gas it has so long been claimed to be."

Not without the forcing of the non-condensing greenhouse gases to sustain it, no. CO₂ provides 80% of that forcing with the other non-condensing GHGs making up the remaining 20%.

The 0.25W/m² is the maximum globally-averaged solar forcing due to orbital variations which are the underlying cause of Milankovitch cycles. My understanding is that this is a fairly straightforward matter of orbital geometry and comes from astronomers or astrophysicists or whatever. It's not a finding of climate science as such.

The 5.35 * ln(C/C₀) formula is an approximation of the CO₂ climate forcing and it comes from Myhre et al 1998.

Why do you claim that the CO₂ increase is not all due to man? We have emitted the equi...

Water vapour is responsible for ~50% of the *current* greenhouse effect with CO2 at ~20% (Schmidt et al 2010).

However, there is 10 times more water vapour than CO₂ in the atmosphere, so by my reckoning CO₂ is 4 times more effective as a greenhouse gas than water vapour. Part of that is because water vapour is largely confined to the troposphere whereas CO₂ is well-mixed throughout the atmosphere.

"I said that a consequence of the paper was that it could not remain as water vapor in the atmosphere sufficient quantity to act as the greenhouse gas it has so long been claimed to be."

Not without the forcing of the non-condensing greenhouse gases to sustain it, no. CO₂ provides 80% of that forcing with the other non-condensing GHGs making up the remaining 20%.

The 0.25W/m² is the maximum globally-averaged solar forcing due to orbital variations which are the underlying cause of Milankovitch cycles. My understanding is that this is a fairly straightforward matter of orbital geometry and comes from astronomers or astrophysicists or whatever. It's not a finding of climate science as such.

The 5.35 * ln(C/C₀) formula is an approximation of the CO₂ climate forcing and it comes from Myhre et al 1998.

Why do you claim that the CO₂ increase is not all due to man? We have emitted the equivalent of 160ppm but atmospheric concentration has only increased by 110ppm, so nature has absorbed 50ppm or around 390 billion tons of our CO₂ to date.

The 'no feedback' warming is a function of the CO₂ forcing (around 4W/m² per doubling, as calculated from the formula above) and the Stefan-Boltzmann law. I don't know of anyone who disagrees with it - even notorious 'skeptics' like Spencer and Lindzen agree with it.

"Then you assume that all of the warming of 0.7C is due to effects of CO2, which is quite an assumption."

Well you're right, to a point - there are lots of other factors involved but it just so happens that the non-CO₂ forcings roughly cancel out, so the net anthropogenic forcing is around the same as the CO₂ forcing -

I will start with your final figure in which you purport to offer up all of the anthropogenic effects on climate and compare them to "all" of the natural effects. Even accepting the treatment of the errors as random in nature and the belief that all effects have been accounted for, the size of the total anthropogenic effect anywhere from 0.6 to 2.4 W/m2, which we have note is a factor of four difference from the low end to the high end. But, we have no real assurance that we are dealing with random errors in gauging these effects here either. If we add up the low value of each anthropogenic effect, we get -0.507 W/m2 or a net cooling effect. Now, I will grant that this is an unlikely outcome that all the errors will be at this end of the range, unless the temptation to show a positive anthropogenic effect was just so great on many scientists who wanted government funding that they just had a strong bias toward showing the applauded effect. But, what I do find easy to believe, because I have little faith in the actual state of the knowledge of some of these effects, is that the anthropogenic effect is significantly smaller than 0.6 W/m2. The catastrophic nature of man's net effect would be hard to maintain at such a level.

This chart of anthropogenic effects also has a ser...

I will start with your final figure in which you purport to offer up all of the anthropogenic effects on climate and compare them to "all" of the natural effects. Even accepting the treatment of the errors as random in nature and the belief that all effects have been accounted for, the size of the total anthropogenic effect anywhere from 0.6 to 2.4 W/m2, which we have note is a factor of four difference from the low end to the high end. But, we have no real assurance that we are dealing with random errors in gauging these effects here either. If we add up the low value of each anthropogenic effect, we get -0.507 W/m2 or a net cooling effect. Now, I will grant that this is an unlikely outcome that all the errors will be at this end of the range, unless the temptation to show a positive anthropogenic effect was just so great on many scientists who wanted government funding that they just had a strong bias toward showing the applauded effect. But, what I do find easy to believe, because I have little faith in the actual state of the knowledge of some of these effects, is that the anthropogenic effect is significantly smaller than 0.6 W/m2. The catastrophic nature of man's net effect would be hard to maintain at such a level.

This chart of anthropogenic effects also has a serious defect on the natural effects side of the equation. It claims that the only natural effect is solar irradiance and that it varies only from 0.06 to 0.30 W/m2. The 0.06 W/m2 is clearly too small for that, especially since the ultraviolet part of the solar spectrum varies quite a bit. Even at 0.3 W/m2, that is a variation of only 0.0009 times the solar radiance. Over the last few decades, the variance has been about 0.3 W/m2, but we have no reason to believe that it cannot be greater than that over a longer time period. If we suppose that it has been in the present range for 30 years, but it had been cooler in the Little Ice Age, then we would have had a gradual warming since the end of the Little Ice Age as the oceans slowly warmed. That would still be a natural effect and one not represented in your table of effects. Neither are effects due to variations in the solar wind and the solar and Earth magnetic fields.

Looking at the Gavin Schmidt (who I trust as far as I can throw an elephant) Science Brief you reference, the spectral flux spectrum shown is unusually unsaturated by either water or CO2. Only the higher wavenumber half of the big notch in the peak is due to CO2 absorption, so I measure the water vapor effect compared to the CO2 effect in this case to be about 6 to 1. Estimating the change due to doubling the CO2 concentration is another matter given the fact that CO2 overlaps water absorption and is itself already at least substantially self-saturating. Adding CO2 has less and less effect, but so does adding water vapor have less and less effect as vapor. But, Schmidt notes that the net effect of clouds is a cooling effect, even if there is also a cloud induced decrease in cooling the surface. He claims a five times multiplier on the CO2 greenhouse effect due to the greenhouse effect of water vapor and clouds, but he then does not subtract the cooling effect both have on incoming solar irradiance, the cloud part of which is larger than the cloud greenhouse effect.

It is interesting that you give the variance due to orbital changes of the Milankovitch cycle as 0.25 W/m2, yet you think a doubling of CO2 would be a warming effect of 4.0 W/m2. A doubling of CO2 would then have 16 times the effect of the Milankovitch orbital effect which causes Ice Ages. Yet, we have had Ice Ages with much higher CO2 than double that of the present concentration! How can that be? This is clear evidence that the net effect of doubling CO2 is being over-estimated badly.

If we add up the low value of each anthropogenic effect, we get -0.507 W/m2 or a net cooling effect. Sure, but that would be way outside any reasonable confidence interval. It would probably be 0.001% or something. The 0.6 to 2.4 range is presumably the 95% range. It would also be hard to explain why we are seeing extremely rapid global warming at exactly the time that humans are pumping large volumes of greenhouse gases into the atmosphere, if it were not those gases causing the warming. Do you have an alternative theory? Some large but completely unsuspected natural warming influence?

Solar physicists estimate that a Maunder Minimum represents a 0.2% reduction in TSI from today's value, which is a 0.48W/m² reduction in incident solar irradiance - significant, certainly, but much smaller than the smallest plausible greenhouse gas forcing of 2.6W/m²... and no-one's arguing that there has been anything approaching that level of variation in solar irradiance in recent decades, so it's hard to see how it could possibly account for the rapid and accelerating warming since the early 20th Century. Indeed, if you are claiming something around zero for feedbacks (which I would argue is physically implausible as well as contradicting all the evidence) then the increase in TSI coul...

If we add up the low value of each anthropogenic effect, we get -0.507 W/m2 or a net cooling effect.

Sure, but that would be way outside any reasonable confidence interval. It would probably be 0.001% or something. The 0.6 to 2.4 range is presumably the 95% range. It would also be hard to explain why we are seeing extremely rapid global warming at exactly the time that humans are pumping large volumes of greenhouse gases into the atmosphere, if it were not those gases causing the warming. Do you have an alternative theory? Some large but completely unsuspected natural warming influence?

Solar physicists estimate that a Maunder Minimum represents a 0.2% reduction in TSI from today's value, which is a 0.48W/m² reduction in incident solar irradiance - significant, certainly, but much smaller than the smallest plausible greenhouse gas forcing of 2.6W/m²... and no-one's arguing that there has been anything approaching that level of variation in solar irradiance in recent decades, so it's hard to see how it could possibly account for the rapid and accelerating warming since the early 20th Century. Indeed, if you are claiming something around zero for feedbacks (which I would argue is physically implausible as well as contradicting all the evidence) then the increase in TSI could only account for, at most, just over 0.1°C of global warming since mid-18th Century. Agreed?

How did you measure the water vapour effect on the IR absorption spectrum? The Schmidt paper argues for a ratio of 2.5:1, not 6:1. Also he finds that the relative contribution to the greenhouse effect (for CO₂, water vapour and clouds) is essentially unchanged in a doubled CO₂ atmosphere, which is the main basis for fast feedbacks being substantially positive. It seems to me that this must necessarily take account of increased cooling from clouds (or at least, it's not apparent from what Schmidt writes that this is not taken into account). Also it's important to remember that those fast feedbacks are going to initiate slower albedo and carbon cycle feedbacks which will amplify anthropogenic warming even more.

It is interesting that you give the variance due to orbital changes of the Milankovitch cycle as 0.25 W/m2, yet you think a doubling of CO2 would be a warming effect of 4.0 W/m2. A doubling of CO2 would then have 16 times the effect of the Milankovitch orbital effect which causes Ice Ages. Yet, we have had Ice Ages with much higher CO2 than double that of the present concentration! How can that be? This is clear evidence that the net effect of doubling CO2 is being over-estimated badly.

My understanding is that previous ice ages (hundreds of millions of years ago) coincided with periods of low atmospheric CO₂ - Richard Alley talks about this in his Bjerknes lecture which you may have seen. Also remember that solar physics argues for a lower TSI the further back in the palaeoclimate record you look, so higher CO₂ could be expected to result in a similar climate to today.

As for the Milankovitch forcing of ≈0.25W/m², that is the initial orbital forcing, not the total forcing as amplified by climate feedbacks, which Hansen calculates as around 7W/m² -

The CO₂ forcing alone (from ice core measurements) is around 2.4W/m², and we know from glacier terminal moraines that the ice albedo feedback would have added substantially to that, even if other feedbacks are less certain. How, then, is it plausible to argue that feedbacks can be small, zero or even negative? To me that makes no sense at all - feedbacks must surely be large and positive. Don't you agree?

The evidence is actually pretty straightforward. The Earth's climate is about 33°C warmer than it would be if infrared radiation (heat) was able to escape from the surface to space unimpeded by the atmosphere ( Joseph Fourier, 1820s ).

Water vapour and CO₂ are the principal greenhouse gases in the Earth's atmosphere which impede infrared radiation from the surface and are therefore responsible for the Earth's elevated temperature ( Tyndall, 1859 ).

Palaeoclimate data shows that climate sensitivity is around 0.75°C/W/m², including only fast feedback processes - water vapour, clouds, aerosols, sea ice etc. ( Hansen et al 2008 ). Thus today's 1.7W/m² of CO₂ forcing can be expected to produce a warming of 1.3°C at equilibrium from fast feedbacks alone. Thermal inertia of the climate system from oceans and ice sheets means that so far we have seen around 0.7°C of this warming, with a further 0.6°C in the pipeline -

However the total greenhouse forcing is already 2.6W/m², which means around 2°C of warming. Once slower feedbacks kick in, from albedo change and carbon cycle feedbacks, warmi...

The evidence is actually pretty straightforward. The Earth's climate is about 33°C warmer than it would be if infrared radiation (heat) was able to escape from the surface to space unimpeded by the atmosphere (Joseph Fourier, 1820s).

Water vapour and CO₂ are the principal greenhouse gases in the Earth's atmosphere which impede infrared radiation from the surface and are therefore responsible for the Earth's elevated temperature (Tyndall, 1859).

Palaeoclimate data shows that climate sensitivity is around 0.75°C/W/m², including only fast feedback processes - water vapour, clouds, aerosols, sea ice etc. (Hansen et al 2008). Thus today's 1.7W/m² of CO₂ forcing can be expected to produce a warming of 1.3°C at equilibrium from fast feedbacks alone. Thermal inertia of the climate system from oceans and ice sheets means that so far we have seen around 0.7°C of this warming, with a further 0.6°C in the pipeline -

However the total greenhouse forcing is already 2.6W/m², which means around 2°C of warming. Once slower feedbacks kick in, from albedo change and carbon cycle feedbacks, warming will be even greater than that.

We can be confident that most of the observed warming since the mid-20th Century is anthropogenic because if only natural influences were affecting the climate, they would have caused cooling since that time, whereas in reality we have seen substantial global warming (Meehl et al 2004) -

Satellite measurements show that less heat is being radiated away to space at the wavelengths associated with CO₂ absorption (Harries 2001), and ground-based measurements show that more heat is being radiated downwards from the atmosphere (Wang 2009), confirming the enhanced CO₂ greenhouse effect. Other evidence includes observations that nights are warming faster than days, and that winters are warming faster than summers (Braganza et al 2003, Braganza et al 2004), both of which are characteristic of an enhanced greenhouse effect. The resultant significant energy imbalance (Murphy 2009) is thus warming the global climate.

This substantial and accelerating anthropogenic warming is reflected in the terminal decline of Arctic sea ice -

...Greenland ice mass -

...Antarctic ice mass -

...and worldwide glacier ice mass -

Its influence is seen in the widespread thawing of Northern Hemisphere permafrost, changes in wind patterns, increases in the incidence of intense precipitation events, and accelerating rise in global sea level -

The warming is evident in shifting of climate zone polewards and uphill, increasing atmospheric water vapour, longer and warmer summers, shorter and milder winters, fewer frosts, increasing drought and changes in thousands of other physical and biological metrics which indicate warming.

Studies of past climate show that changes in the level of atmospheric CO₂ are intimately linked to large changes in temperature, for example the multi-thousand year cycles of ice age and interglacials in the last million years. In these natural cycles, small changes in solar irradiance are amplified many times by the enhanced greenhouse effect of increasing greenhouse gases, together with other positive feedbacks, and this is enough to take the planet from an ice age with mile-thick ice sheets over much of the North America and Northern Europe, to today's much warmer state with Northern Hemisphere ice largely confined to the Arctic.

Hence we can be confident that today's man-made changes in greenhouse gases will also have a large effect on global climate, with natural feedbacks acting to amplify rather than minimise global warming. Modern climate observations reinforce this conclusion that natural feedbacks will be overwhelmingly positive rather than negative, and thus will amplify warming. Given the proven sensitivity of the global climate to past natural forcings, it is not likely that it will react differently just because it is now human activity raising the CO₂ level rather than natural changes. Modern observations of global temperature changes also rule out a very low climate sensitivity, whereas it has not been possible to rule out very high sensitivity.

With anthropogenic warming running at or above the worst case scenarios, and the climate already changing in many different measurable ways, the prospect of retaining anything similar to the climate in which modern human civilisation developed looks bleak. It's notable that we've just had the deepest and longest solar minimum for a century and yet seen no cooling at all - it's been completely wiped out by anthropogenic global warming. During the next few years we will have continuing and accelerating AGW, and rising solar irradiance, so the warming will be that much the greater.

Under a 'business as usual' emissions scenario, by 2020, global temperature will have risen by around another 0.3°C above today's value. By 2030, it will be at least 0.6°C above today's value, and by 2040 it will have risen by at least 1.0°C above today's value. By mid-21st Century, we will have exceeded 2°C above mid-20th Century temperature, and probably by a wide margin as carbon cycle and ice albedo positive feedbacks will be substantially amplifying anthropogenic warming, and the Arctic ocean will be largely ice-free in the summer by around 2015. This will have devastating effects on world agriculture and fresh water supplies. Drought will continue to increase, forests will continue to die off and burn, and ocean dead zones will continue to spread. Accelerating sea level rise accompanied by intensifying storms will cause increasing coastal damage and likely loss of life. Millions of humans will die from famine, thirst, resource wars and natural disasters.